Wetting agents for non-aqueous dispersions

ABSTRACT

This patent comprises novel non-aqueous dispersions of polar solids in non-polar organic liquids containing a wetting agent which is:   WHEREIN R1 and R2 are monovalent organic groups such as alkyl or aryl, R3 is an aliphatic or aromatic hydrocarbon structure to which the ureido groups are attached, and n is an integer of from 1 to about 4;   WHEREIN R4 is hydrogen or monovalent organic, usually lower alkyl, and R5 is monovalent organic such as alkyl or phenyl;   WHEREIN R6 is hydrogen or lower alkyl and R7 is a monovalent organic group such as alkyl, phenyl or aryl;   WHEREIN R8 and R9 are monovalent organic groups such as alkyl or aryl.

United States Patent [191 Bruenner [4 June 25, 1974 1 WETTING AGENTS FORNON-AQUEOUS DISPERSIONS {75] Inventor: Rolf S. Bruenner, Orangevale,Calif.

[73] Assignee: Aerojet-General Corporation, El

Monte, Calif.

22 Filed: Oct.23, 1970 [21 App1.No.:83,473

[5 6] References Cited UNITED STATES PATENTS 2,993,044 7/1961 Applegathet a1. 260/2472 3,184,301 2/1965 Martin 7l/2.6

Primary Examiner-M0rris Liebman Assistant Examiner-Richard ZaitlenAttorney, Agent, or Firm-E. O. Ansell; M. C. Jacobs [57] ABSTRACT Thispatent comprises novel non-aqueous dispersions of polar solids innon-polar organic liquids containing a wetting agent which is:

wherein R and R are monovalent organic groups such as alkyl or aryl, Ris an aliphatic or aromatic hydrocarbon structure to which the ureidogroups are attached, and n is an integer of from 1 to about 4;

intranets wherein R is hydrogen or rnonovalent organic usually loweralkyl, and R is monovalent organic such as alkyl or phenyl;

(III) 7 wherein R is liy drogen or lower alkyl and is a mo novalentorganic group such as alkyl, phenyl or aryl;

wherein R and R are monovalent organic groups such as alkyl or aryl.

2 Claims, 11 Drawing Figures PATENTED JUN25 74 NOMINAL VISCOSITY (cp)IxIo sum 02 or 11.

RESPONSE OF COATED UFAP T0 WETTING AGENTS PREMIX TT'b COATED UFAP, |6%HTPBTSINCLAIR R-45), 7% TDP MINUTES (0.5 G/IOOG PREMIX) FlG.-2

INVE/VIOR ROLF S. BRUENNER JmrmwIw/E A TTORNEYS PROPELLANT VISCOSITY ASA FUNCTION OF SHEAR STRESS N0 CURING AGENT PATENTED JUH25 T974 sum 11 0F11 15 2o APPLIED SHEAR STRESS, DYNES/CMZXIO'3 INVENTOR 2: ROLF s.BRUENNER (9 jmafikwzwuotfi LL. ATTORNEYS BACKGROUND OF THE INVENTIONWetting agents are used to reduce the viscosity of suspensions, disperseparticles and break-up agglomerates, stabilize very small particles toprevent regrowth, and improve the grinding of solids to collodialdimensions.

Wetting agents reduce the strong forces between highly polar particlessuspended in an unpolar liquid, which are responsible for the highviscosity and thioxtropy of such suspensions. They attach themselves tothe solid with the polar part of the wetting agent molecule, the unpolarhydrocarbon part forming the outer surface of the adsorbed orientedlayer. By this steric separation the forces between particles arereduced to nearly the small forces existing between hydrocarbonmolecules (dispersion forces). At the same time the wetting agent helpsto de-agglomerate (deflocculate) the solids during mixing. Very smallparticles are stabilized, i.e.. their higher solubility is reduced. Thisis important, even if only a very small solubility of the solid in thedispersion medium existed, to prevent growth of larger particles at theexpense of the smaller ones. The solubility of particles of radius r,L,, is approximately described by L, L,, exp(2M/RTp'7/r), where L is thesolubility of the substance in bulk, p density of the disperse phase, Mits molecular weight, R gas constant, T absolute temperature (K) and yinterfacial tension between surface of particle and solution. If 7 isthe interfacial tension and L the solubility of a particle with radius rwithout a wetting agent, and 7 L the respective quantities with wettingagent, then mr L r.U/ PI P (7o 7U] mc be the smaller as to L, thesmaller y becomes.

Wetting agents are useful in the preparation of collodial sizeparticles, where they assist the primary processes of disruption ofparticles in liquid media as well as preventing their re'aggregation.Such effects have been investigated and shows, for example, that theyield stress of single crystals of tin immersed in an un polarhydrocarbon oil could be decreased by as much as 50 percent in presenceof small amounts of oleic acid and similar materials. Comparable effectswere found on the breaking stress of glass fibers, immersed in wa ter,in presence of anionic and cationic wetting agents. In contrast toaqueous media, wetting agents in nonaqueous media are more specific tothe system involved. For rocket propellant slurries the performance ofthe wetting agent will depend essentially on the chemical nature of thebinder, which determines the interaction of filler-binder as well asfiller-wetting agent; e.g. wetting agents which perform well in morepolar systems, like polyether prepolymers, will not necessarily do so inless polar systems, like polybutadiene prepolymers.

For this reason one cannot rely on wetting agents known to be effectivein polyetherbased polyurethane propellants, nor on the wide spectrum ofavailable wetting agentsmost of which are intended for aqueous systems.

The present invention involves new types of structures and some generalprinciples in the use of wetting agents to reduce viscosity and improveflow characteristics, particularly in high viscosity propellant systemssince these wetting agents are quite effective in the presence of veryfinely ground oxidizers. Viscosity measurements in selected systemsshowed that the wetting agents of this invention surpass the previouslyknown diethanolamide of oleic acid and pure lecithin.

SUMMARY OF THE INVENTION Briefly, the present invention comprises noveln0naqueous dispersions of polar solids in non-polar organic liquidscontaining a wetting agent which is:

wherein R and R are monovalent organic groups such as alkyl or aryl, Ris an aliphatic or aromatic hydrocarbon structure to which the ureidogroups are attached, and n is an integer of from I to about 4;

itmitsst.

wherein R is hydrogen or lower alkyl and R is monovalent organic;

wherein R and R are monovalent organic groups such as alkyl or aryl. Ingeneral, R R R R R R R R and R contain from 1 to about 20 carbon atoms.

It is an object of this invention to provide a novel class of wettingagents for non-aqueous dispersions.

It is another object of this invention to provide novel dispersionscontaining wetting agents.

It is a further object of this invention to provide a novel propellantformulation having improved properties.

These and other objects and advantages of this invention will beapparent from the following detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The wetting agents of formula Iare prepared by reacting two moles of a secondary amine of the formula:

with one mole of an organic polyisocyanate of the formula:

The wetting agents of formula II are prepared by re 5 with one mole of apolyisocyanate of the formula:

acting a mole of the compound of the formula:

R4 in;

with three moles of an organic monocarboxylic acid of l5 the formula:

0 Rri. JOH.

The wetting agents of formula III are made by reacting one mole ofasulfone of the formula:

or in fL-Ionrcrn-N lml with two moles of a monocarboxylic acid of theformula:

O RFC-01 To demonstrate wetting agents it was found most convenient tomeasure the viscosity of suspensions, e.g. ultrafine ammoniumperchlorate (UFAP) in mineral oil (liquid petrolatum), which combines asuitable viscosity with inertness and low volatility, and comes close toa hydrocarbon (hydroxy-terminated polybutadiene) binder. The mixtureused consisted of 625g BDB coated UFAP (0.5a) in 1 ltr. mineral oil, ltsconsistency is like vaseline and it does not settle nor flow withoutvibration, but with wetting agents it will, and

viscosities as low as 1,500 centistokes can be obtained,

which allow quantitative measurements in Oswald type viscosimeters.

For measurement purposes, 4 grams of above suspension were mixed with 40mg (1%) of the wetting agent to be tested. Changes in fluiditywerejudged only qualitatively by the flow behavior. Only those wettingagents, which made the suspension flow without vibra' tion weresubjected to quantitative viscosity measurements. Table I summarizes theresults thus obtained with a variety of wetting agents. For each classof compounds a typical example is given, usually one that produces thestrongest effect within that class as to lowering viscosity (calledOptimal Effect" in Table l). A very weak" effect means that the mixturebecomes less thioxtropic, but still does not flow without vibration,whereas a weak effect means that flow occurs without vibration, (i.e.the static" yield value is zero), but the viscosity is still high.

TABLE I.-TYPES OF WETTING AGENTS AND THEIJIIIIE EFFECTS ON UFAP SLURRIESIN A HYDROCARBON Class of compounds Examples Optimal etfect CationicWetting agents:

Substituted ammonium salts Very weak.

H:tCira)zC 2 C1 Fatty amines HaJCniN(C :)2 Weak. Anionic wetting agents:

Alkane sullonates Twitchclls base 8240 Medium. Fatty acids and theirsalts- Oleic acid Weak. Zwitterionic wetting agents:

Amine oxides 0 None.

H:7CrsN(CH2CH2OH)2 Betalnes D0.

HzsCi2N( Ha)2CH2-CH:-COO- Sulfobetalnes Do.

H 10isN(CH3)a-(CH;);-SO,-

Phosphobetalnas U Lecithin Strong. Nonlonlc wetting agents:

Fatty nltrlles i n-Undecyl-cyanide i None. Fatty alcohols i OleylalcohoLD0. Fatty esters. Sorbitantrioleate Weak, Polyethers Polyethylene glycoldi-oleate Medium. Amide type:

Carboxylic acid amides Oleoyl-N(CH-3CH; 0H)1 Do.

Carboxylic acid amide-esters". R (131E; Do.

E R, R=C O-N-CHCH:-O-oleoyl l R Urethanes C H; w

Table l Continued Class of compounds Examples Optimal etleet Ureas:

Mono-areas HIC4NHCON(CI3H37)2 D0- Bis-ureas Very strong.

H1O NH-C ON(0leyl)z Tris-ureas R Do.

R R=NH-C 0N(oley1)z Bis-urea-esters C H; Strong.

OzNN[--CH;CH2NHC ONHCHCHz-Ooleoyl]2 Thtoureas S=C[N (ole Very Weak.Phosphomtrilamides [PN(NHC"H None.

Phosphoamides /C H; D0.

Phosphoamide-esters (3H Strong.

0 P -NHCHCH- Ooleoyl Phosphotlreides 0P[NH-CO-N(o1ey1i1]; Very strong.slllcoureides Si[NHCO-N(oleyl)z 4 Strong- Ammoestersulfones01S[-CHgCHg-NHCHzCHz-O-Ole0ylh D0.

Very few of the ionic types are effective. notably Twitchells Base 8240,an alkane sulfonate, and lecithin, a phosphobetaine. It may be that thislack of effectiveness is due to insolubility in the dispersion medium,since the effective ones (Twitchell Base and lecithin) are quite solublein mineral oil. However, solubility is usually good for the nonionicwetting agents, but yet there are large differences in effectiveness,which can be ascribed to specific chemical structures. It is quitestriking that all of the strong wetting agents belong to the amide type;even lecithinmay be counted as a member of this group, though its amidenitrogen carries a full positive charge. Still other requirementsapparently have to be fulfilled for an amide to be a good wetting agent,since some classes of amides are completely ineffective.

Comparing compounds containing only one urea group (mono-ureas) withthose containing two or more urea groups (bis-urea etc.) it can be seenthat the first ones are hardly effective, whereas among the latter thestrongest wetting agents are found. It seems then that for strongadsorption at least two polar groups are necessary. Similar commentsapply to the case of simple phosphoamides vs. phosphoamide-esters. whereonly the latter are good wetting agents.

Within the class of bis-ureas a somewhat more detailed study has beenmade on the influence of certain substituents on the performance of suchcompounds as wetting agents. The general formula for these bis-ureas canbe written as:

lfR. R H was kept constant, a variation of R indicates a slight changein activity. Much more dramatic changes are observed, when R; is keptconstant and R and R are varied.

Three series of compounds have been synthesized with respectively. R,was equal to R and varied from C H through C H C H C H to C H With C H-there is still optimal efficiency, but it is falling off rap idly withdecreasing hydrocarbon chain length and is practically zero for C H WithR CH R and R2 C gH37,

and C4Hg respectively no activity was found with these compounds. Thesame was true for R CH 6-. R H and R2 CrgHgg C16H33 and CmH Superiorwetting agents were obtained when R R (CH TABLE II.VISCOSITIES OF ANUFAP (BDB-COATEDyMlNEPJL OIL SLURRY WITH 0.5%

ADDITIVE Viscosity (centi- No. Compound stokes) CH; NHCON(oleyl);

2 OP[NHCON(o1eyl)1 1 1,520 3 O;NN[CH:C r-NHCON(iey1)1]1 1,581

CH: H NHCON O18Y1)1] RC HrCH-C HrC (CHEM-C Hz-CHr-R; R:-NHCON(C| H;7):

[ CH1 NHC ON(oley1):]

CH; R=NHCON(o1ey1) R H :NHC 0N C|1H11 1 R R=NHC ON(01ey1):

11 Pure lecithin 1, 780

1 Oleyl designates C H1 CH=CH C Hr CHa.

12 cm -mac omcmm] 1,820

R; R=-NHC ON(C1:H:$)1

14 OP["'NHCON(CHH25)1]J 1,960

15 (iJH: 1,970

0 P [-NH-C HC FIFO-01903 1]; 2

16 1 OzNN[-CH1CH1NHCON(C11H 5):]z 1,985

17 CH NHC ON 18 1 Hydroxylated lecithin 2,180

O1NN[CH3CH1NHC ONH--C HC H;-Oo1eoy1]:

20 0CNHC H31\ 2,290

N-C r--/:

21 P[NHCON(C11H15):]3 2, 500

HQ, R=CONHC H-C H1O-ole0y1 23 O:S[CHI-CHr-NHCHr-CH;-OO1e0y1]1 1. 2.560Si[NHCON(C gH15)g]4 1 2,610 Lecithin as received (57% solution in oil)v2,950 26 Twitchell Base 8240 22,800

With the same system and method of dependence of viscosity on wettingagent concentration was measured. The data show (F G. 1) that with thestronger wetting agents a minimum viscosity will be obtained within arather small concentration range, which is the same for both wettingagents shown (lecithin and Compound No. l of Table II). The differencein their effectiveness shows up in the different concentrations, atwhich this level of minimum viscosity is reached. Weaker wetting agents(Compound No. 23 of Table II) do not only require higher concentrationsfor minimum viscosity, but apparently they also do not reach the samelow level of viscosity obtained with stronger wetting agents. Furtherstudies on such wetting agents revealed that they are not specific forBDB coated UFAP, but work as well with uncoated NH CIO In fact, they arenot even specific for NILCIO or NHfsalts. The viscosity of suspensionsof powdered KCI or collodial silica in mineral oil as shown in Table IIIis just as well reduced by them, and this seems to hold for all polarsolids.

TABLE 'r'rr-vr'scosi'rias M A COLLOIDAL so, small? IN MINERAL OIL WITH2% ADDITIVE Viscosity Compound (centistokes) #22 of Table II 728. #15 ofTable II 750. Diethanolamide of oleic acid (DEO") 772. #5 of Table II805.

Lecithin (3.5%, corresp to 2% pure) l3 0! Table II Hydroxylated lecithinD0.

Cabosil:mineral 0il=8z100 b.w.; this mixture has a Vaseline-likeconsistency.

Most critical is the polarity of the dispersion medium, inasmuch as itrequires a certain balance of the polar and unpolar part of the wettingagent. thereby narrowing the range of usable wetting agents. To put itit other words. these wetting agents are more specific in respect to thedispersion medium than in respect to the dispersed solids.

The binder systems considered for UFAP propellants consist mostly ofpolybutadiene prepolymers with functional terminal groups. such ascarboxy-terminated polybutadiene (CT PB) and hydroxy-terminatedpolybutadiene (HTPB). Due to their higher viscosity, dispersions of UFAPin such prepolymers can no longer be measured with Oswald typeviscometers and one has to switch to viscometers with rotating parts,such as the Brookfield. In case of thixotropic systems the yield valueis easily reached in the immediate vicinity of the rotating spindle. butwill spread out with time to more remote layers, so that a decrease ofviscosity with time will be found. It is. therefore. more appropriate.to compare viscosity time curves than single viscosity data. Preferablyspindle sizes and rpms should be kept constant. unless correlationfactors have been established for the particular system.

Under such conditions wetting agents have been tested in differentbinder systems. An example is shown in FIG. 2, where the test vehiclewas a mixture of 77 percent coated UFAP, l6 percent hydroxy-terminatedpolybutadiene (HTPB) and 7 percent isodecyl pelargonate (lDP). Thewetting agents were tested at a concentration of 0.5g/l00g premix.

In this case the test system is not appreciably thixotropic as judgedfrom the more or less horizontal viscosity-time curves. It is seen thatthe order of effectiveness has somewhat changed compared with that inthe mineral oil-UFAP system (Table II).

A more accurate measurement of viscosities is achieved, if underequilibrium conditions the dependence of viscosity on shear stress isobtained as with the Rotovisco" viscometer. Such measurements have beenmade with HTPB propellant and selected wetting agents. The compositionof the propellant was as follows:

Solids: 8471 (oxidizer and metallic fuel) Binder: I69; HTPB 9.575%Isophorone diisocyanate (IPDI) 0.9259 Ballistic additive 591' Wettingagent 0.5

For wetting agents with functional groups. like DEO, the HTPB/IPDI ratiowas adjusted correspondingly. Since the OH groups of thehydroxy-terminated polybutadiene are primary and its averagefunctionality is about three, the curve reaction is relatively fast andincreases of viscosity within one hour can be significant. For thisreason propellant viscosities were measured 1.5 and 2.5 hours aftercuring agent addition. The results of these measurements are shown inFIGS. 3IO.

From FIGS. 3 and 4 it is at once obvious that lecithin apparentlyaccelerated the cure reaction, which more than compensated its effect asa wetting agent. Very much the same situation is found with lecithine inan identical binder without any solids. As seen from FIGS. 3l0, verysubstantial decreases of propellant viscosity can be realized by some ofthe wetting agents tested. In one or the other case a certaindeceleration of the cure reaction rate may also be involved. but allpropellants cured to essentially the same hardness within a few days.That both phenomena may be operative is made likely by results withpropellants. where the curative was held out (replaced by an equalvolume of hydroxyterminated polybutadiene) (see FIG. 11). There is stillthe effect of the wetting agents showing in the reduced viscosity overthe control, but at the same time the viscosity of the control isconsiderably lower than that of a control with curvative (note that thescale in FIG. 11 is different from preceding figures).

The burning rate of a control propellant of above composition is about5.3 in./sec at 2,000 psi and is not different within the accuracy ofCrawford bomb solid strands burning rate measurements from propellantscontaining 0.5 percent of the wetting agents investigated.

From the data presented it can be seen that substituted bisandpoly-areas, certain ureides, and aminoester derivatives, such as therespective amides. are very useful as processing aids.

PREPARATION OF WETIING AGENTS All of the bisand poly-ureas as well asureides were prepared by the clean and quantitative addition reactionbetween isocyanate, and amines. which takes place almost instantaneouslyeven at room temperature.

Equivalent amounts of isocyanate and amine were dissolved separately indry benzene and the isocyanate solution added to the amine solutionunder stirring. The solvent was then evaporated at ambient pressureuntil the temperature of the residue reached about 100C; 5 the producewas stripped under vacuum. After this a sample of the product was eitherdissolved in or extracted with methanol and the pH of the methanolicsolution checked, which is normally between 6 and 7 if all amine is usedup. Recrystallization and distillation 10 cannot be used in most casesfor purification of the product; especially products derived fromdi-oleylamin or oleic acid are liquid or semi-liquid, but also most ofNumber of Starting compounds for substituted ureas and ureides compoundas Appearance of rein Table II Amine Isocyauate action product i Viscousto semi- IlN-CIiz-CH=CII(C119 0111 CH NC 0 solid yellow-brown a 2product.

("Armeen 2-0). "Isonate 125M".

2 do OP(NCO)1 Yellow liquid of medium viscosity. 3 ..do OzN-H(CHzCHr-NC0); Yellow waxy solid.

XIII-Dilsocyanate 4 do Amberoolored 0CN- CH3, liquid of mediumviscosity. l NCO TDI.

5 do Viscous, amber- CH, -Qa NC 0 colored liquid.

Naeoonate:Hl2".

7 do f Amber-colored O CNCHz-5NCO, semi-solid products.

s d Bufl colored waxy solid. CH1

NCO 1 l'sonate 136T".

10 do NC 0 Yellow, soft solid.

0 CN H NC 0 C'Il".

s amcnnuii our White, waxy 301m.

(Armeen 2HI). (lJ

0CN-CH2 II-CH2-C(CHa)2CHz-CHz-NCO TMD-1".

9 d0 NC 0 Brittle white solid.

C'II".

12 .410 White solid.

0 CN-CHz-NC O,

HDI.

l3 HN(CuHz5)2 CH; Viscous yellow (Arrneen 2C"). liquid.

OCN- v TDI.

i4 do OP(NCO); Turbid liquid. 16 do OzN--N(CHzCH2-NCO)2XIII-Diisocyanate Light yellow, waxy solid.

V V g V V rare rv caarauea Number of Starting compounds for substitutedureas and ureides compound as Appearance of rein Table II AmineIsocyanate action product 17... do 'wiiit, way sand.

C NCH2 N C 0 A H DI.

21 do P(NCO) Turbid liquid. 24 do Si(NCO) Turbld liquid,

slightly basic.

HmCmNCO Bufi Solid.

-NHCHz-CH2NH- Starting compounds for amidoand amino-esters* Aziridinederivative Carboxylic acid 15 C H CH Oleic acid Amber-colored viscousliquid. 0 P N (MAPO).

19 CHCH d \ery viscous yellow liquid. O2NN CH2CH2NHC ON R do Yellow,waxy solid.

I C H C 2H5 R'Q R= c ON 1 CH R 23 CH (1() Yellow, vicsous liquid.

These materials have been made by neat reaction of equivalent amounts ofthe starting compounds listed.

The wetting agents of formulaeland [V are prepared is an aliphatic oraromatic hydrocarbon structure to in accordance with the proceduredescribed in U.S. which the ureido groups are attached, and n is aninte- Pat. No. 3,184,301. get of from 1 to about 4.

The wetting agents of formulae II and III are pre- 2. The dispersioncomprising ultrafine particle of ampared in accordance with U.S. Pat.No. 2,915,480. monium perchlorate in a hydroxy-terminated polybutaHaving fully described the invention it is intended diene polymercontaining a wetting agent which is: that it can be limited only by thelawful scope of the appended claims.

1 claim:

1. Novel non-aqueous dispersions of polar solids in E f? E non-polarorganic liquids containing a wetting agent which is: R2 R2 n R2 nwherein R and R are monovalent organic groups, R is an aliphatic oraromatic hydrocarbon structure to which the ureido groups are attached,and n is an integer of from 1 to about 4.

wherein R and R are monovalent organic groups, R =1

2. The dispersion comprising ultrafine particle of ammonium perchloratein a hydroxy-terminated polybutadiene polymer containing a wetting agentwhich is: